BMW /5 motorcycles came equipped with two styles of mirrors, both shown in the photo on the right. The longer stem mirror, mounted on the clutch side of the handlebar, is the proper mirror for this motorcycle. The reason is that this bike is equipped with the low-rise handlebars, also called European Style bars, or "Euro" bars.
The mirror on the throttle side of the handlebars is the short-stem mirror for US style handlebars. These bars have a higher rise to them, and therefore, the mirror stem doesn't need to be as long.
From the factory, /5 motorcycles sold in the U.S. came with a left side mirror as stock. The right side mirror was optional. By using two different mirror stem lengths, the rider can usually see something in one mirror or the other as the mirrors don't vibrate at the same frequency.
Aftermarket mirrors are often seen on /5s. The bar-end style mirror fits on the ends of the handlebars, as seen on this R75/5, owned by Lou in Boca. One disadvantage to bar-end mirrors is when the bike falls over, they may break when they hit the ground.
Aftermarket Bar-end mirrors from Constructor's Racing Group are made of machined aluminum, anodized black. They feature replaceable mirror glass, and are of very high quality. They are expensive, however, at about $65 per mirror, plus $20 adapter. Easy to install, and rock steady at speed. Easy to adjust, and they stay adjusted. There are meant for modern sport bikes, but work on a /5. View 2, View 3.
Napolean Ear End mirrors are common, less expensive and have a more square shape. They are available in both chrome and black.